Liquid-crystal polyester resin

ABSTRACT

The present invention provides a liquid-crystalline polyester resin which comprises monomer units derived from 2-hydroxy-3-naphthoic acid and/or 2-hydroxynaphthalene-3,6-dicarboxylic acid in an amount of 1-5000 mmol % based on the total monomer components of the resin and an alkaline metal compound in an amount of 10-3000 ppm as alkaline metal based on the total monomer components of the resin. The liquid-crystalline polyester resin of the present invention has good colorability, improved heat resistance and good mechanical properties.

TECHNICAL FIELD

The present invention relates to a liquid-crystalline polyester resin.More particularly, it relates to a liquid-crystalline polyester resinwhich has good colorability, improved heat resistance and goodmechanical properties.

BACKGROUND ART

Thermotropic liquid-crystalline polyester resin (which is calledliquid-crystalline polyester resin or LCP hereinafter) is used not onlyfor molded articles but also for a variety of products such as fibersand films because of its good properties including heat resistance,mechanical properties such as rigidity, chemical resistance anddimensional accuracy. Particularly, parts used in personal computers andmobile phones are highly integrated and the art wishes to use downsized,thinner and smaller parts. In the information and telecommunicationfields, very thin parts, as thin as 0.5 mm or less of the thickness, aresometimes required. Based on the excellent molding properties of theLCPs including good flowability and less flash development compared tothe other thermoplastic resins, consumption of the LCPs has beenincreasing.

On the other hand, there still exists a need for improving flowability,heat resistance and mechanical properties of liquid-crystallinepolyester resins and there have been many proposals about theimprovement of LCP. For example Japanese Patent Application Laid OpenNo. 511573/1996 discloses a liquid-crystalline polyester resincomposition with improved heat resistance made by admixing an alkalinemetal within certain kinds of monomers and polymerizing them.

However there is still a room for improvement with respect to uniformcolorability and restoring the color of colorant such as carbon black,azo pigment and the like. Accordingly, in the field that requiresuniform colorability and bright coloration, the use of LCP has beenlimited.

An object of the present invention is to provide a liquid-crystallinepolyester resin with good colorability, an improved heat resistance andsatisfactory mechanical properties.

SUMMARY OF INVENTION

The present inventors have found that a liquid-crystalline polyesterresin with good colorability, improved heat resistance and goodmechanical properties can be obtained by copolymerizing a small amountof 2-hydroxy-3-naphthoic acid and/or2-hydroxynaphthalene-3,6-dicarboxylic acid with other polymerizingmonomers and admixing a certain amount of an alkaline metal compoundwith the copolymer and have completed the invention.

Accordingly, the present invention provides a liquid-crystallinepolyester resin with good colorability, improved heat resistance andgood mechanical properties, which comprises monomer units derived from2-hydroxy-3-naphthoic acid and/or 2-hydroxynaphthalene-3,6-dicarboxylicacid in an amount of 1-5000 mmol % based on the total monomer componentsof the resin and an alkaline metal compound in an amount of 10-3000 ppmas alkaline metal based on the total monomer components of the resin.

BEST MODE FOR CARRYING OUT THE INVENTION

The liquid-crystalline polyester resin of the present inventioncomprises, as its structural components, monomer units derived from2-hydroxy-3-naphthoic acid and/or 2-hydroxynaphthalene-3,6-dicarboxylicacid in an amount of 1-5000 mmol %, preferably 10-4000 mmol % and morepreferably 50-3000 mmol % based on the total repeating units of monomercomponents of the liquid-crystalline polyester resin. In the case when2-hydroxy-3-naphthoic acid and 2-hydroxynaphthalene-3,6-dicarboxylicacid are used in combination, their weight ratio may preferably be10/90-90/10, more preferably 20/80-80/20.

2-hydroxy-3-naphthoic acid can be prepared by reacting 2-naphthol withsodium hydroxide to give sodium 2-naphtholate, reacting the sodium2-naphtolate with carbon dioxide under an increased pressure, andseparating the product by means of acid crystallization. The product mayoptionally be purified.

2-hydroxynaphthalene-3,6-dicarboxylic acid can be prepared by the methoddescribed in WO 98/17621 (Japanese Patent Application No. 519205/1998),i.e. reacting potassium 2-naphtholate with carbon dioxide, separatingthe product by means of acid crystallization, and optionally purifyingthus obtained product.

The liquid-crystalline polyester resin of the present invention furthercomprises an alkaline metal compound in an amount of 10-3000 ppm,preferably 20-2000 ppm, more preferably 30-1000 ppm as an alkalinemetal.

Examples of alkaline metals include lithium, sodium, potassium, cesiumand rubidium. Among the above, sodium and potassium are preferable, andpotassium is most preferable.

Alkaline metal compounds in LCP are in the forms of salts. Examples ofsuch salts include sulfate, carbonate, bicarbonate, nitrate, carboxylateand haloid of alkaline metal. Among the above, carboxylate, sulfate andcarbonate are preferable. As carboxylate, salts with aliphaticcarboxylic acid having 2 to 6 carbon atoms and that introducingcomponent of the liquid-crystalline polyester resin are preferable.Examples of such carboxylate include acetate, 4-hydroxybenzoate,2-hydroxy-6-naphthoate, 2-hydroxy-3-naphthoate,2-hydroxynaphthalene-3,6-dicarboxylate and salts of polymerizingmonomers from which other aromatic carbonyl repeating units are derivedand the like.

The mean volume diameter of alkaline metal salt in the polyester resinis preferably 0.01-500 μm, more preferably 0.05-150μm.

The liquid-crystalline polyester resin of the present invention is notspecifically limited and may be any polyester resin that exhibitsanisotropic melt phase and is called as thermotropic liquid-crystallinepolyester resin by those skilled in the art.

The anisotropic melt phase can be confirmed by means of conventionalpolarized light system using orthogonal light polarizer. In more detail,the sample on the hot stage under nitrogen atmosphere may be observed.

The liquid-crystalline polyester resin of the present invention maypreferably be a liquid-crystalline polyester resin or aliquid-crystalline polyester amide resin which exhibits anisotropic meltphase and comprises structural monomer unit(s) selected from the groupconsisting of aromatic hydroxycarboxylic acid, aromatic dicarboxylicacid, aromatic diol, aromatic hydroxy dicarboxylic acid, aromatichydroxyamine, aromatic diamine, aromatic aminocarboxylic acid. Among theabove, aromatic diol, aromatic dicarboxylic acid, aromatichydroxycarboxylic acid and aromatic hydroxydicarboxylic acid arepreferable.

Examples of the aromatic hydroxycarboxylic acids include4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid,2-hydroxy-6-naphthoic acid, 2-hydroxy-5-naphthoic acid,2-hydroxy-3-naphthoic acid, 4′-hydroxyphenyl-4-benzoic acid,3′-hydroxyphenyl-4-benzoic acid, 4′-hydroxyphenyl-3-benzoic acid, andalkyl-, alkoxy- or halogen-substituted derivatives thereof as well asester forming derivatives thereof. Among the above, 4-hydroxybenzoicacid and 2-hydroxy-6-naphthoic acid are preferable in terms ofcontrolling the properties and the melting point of the resultingliquid-crystalline polyester resin.

Examples of the aromatic dicarboxylic acids include aromaticdicarboxylic acid such as terephthalic acid, isophthalic acid,2,6-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid,2,7-naphthalenedicarboxylic acid, 4,4 -dicarboxybiphenyl, bis(4-carboxyphenyl) ether, bis (4-carboxyphenoxy) butane, bis(4-carboxyphenyl) ethane, bis (3-carboxyphenyl) ether, bis(3-carboxyphenyl) ethane and alkyl-, alkoxy- or halogen-substitutedderivatives thereof as well as ester forming derivatives thereof. Amongthe above, terephthalic acid and 2,6-naphthalenedicarboxylic acid arepreferable in terms of controlling the mechanical properties, heatresistance, melting point and moldability of the resultingliquid-crystalline polyester resin to the desired level.

Examples of the aromatic diols include aromatic diol such ashydroquinone, resorcin, 2,6-dihydroxynaphthalene,2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,40-dihydroxybiphenyl, 3,3′-dihydroxybiphenyl, 3,40 -dihydroxybiphenyl,4,4′-dihydroxybiphenylether, bis (4-hydroxyphenyl) ethane and alkyl-,alkoxy- or halogen-substituted derivatives thereof as well as esterforming derivatives thereof. Among the above, hydroquinone and4,4¹-dihydroxybiphenyl are preferable in terms of the good reactivityduring the polymerization process and the good properties of theresulting liquid-crystalline polyester resin.

Examples of the aromatic hydroxyamines, aromatic diamines and aromaticaminocarboxylic acids include aromatic hydroxyamine such as4-aminophenol, N-methyl-4-aminophenol, 3-aminophenol,3-methyl-4-aminophenol, 4-amino-1-naphthol, 4-amino-4′-hydroxydiphenyl,4-amino-4′-hydroxydiphenylether, 4-amino-4′-hydroxybiphenylmethane,4-amino-4′-hydroxybiphenylsulfide, aromatic diamine such as1,4-phenylenediamine, N-methyl-1,4-phenylenediamine, N,N′-dimethyl-1,4-phenylenediamine, 4,4′-diaminophenylsulfide(thiodianiline), 2,5-diaminotoluene, 4,4′-ethylenedianiline,4,4′-diaminodiphenoxyethane,4,4′-diaminobiphenylmethane(methylenedianiline),4,4′-diaminodiphenylether(oxydianiline), 4,4′-diaminodiphenylsulfone,aromatic aminocarboxylic acid such as 4-aminobenzoic acid,6-amino-2-naphthoic acid, 7-amino-2-naphthoic acid and ester formingderivatives thereof.

Examples of the aromatic hydroxydicarboxylic acids include2-hydroxynaphthalene-3,6-dicarboxylic acid, 4-hydroxyisophthalic acid,5-hydroxyisophthalic acid and alkyl-, alkoxy- or halogen-substitutedderivatives thereof as well as ester forming derivatives thereof.

In addition, unless impair the object of the present invention, theliquid-crystalline polyester resin of the present invention may becopolymerized with other monomers than described above. Examples of suchmonomers include alicyclic dicarboxylic acid, aliphatic diol, alicyclicdiol, aromatic mercaptocarboxylic acid, aromatic dithiol, aromaticmercaptophenol, aromatic mercaptonaphthol and the like. The proportionof these additional monomers to the total amount of aromatichydroxycarboxylic acid, aromatic dicarboxylic acid and aromatic diol ispreferably no more than 10 mol %.

Examples of alicyclic dicarboxylic acids, aliphatic diols and alicyclicdiols include alicyclic dicarboxylic acid such as hexahydroterephthalicacid; alicyclic diol such as trans-1,4-cyclohexanediol,cis-1,4-cyclohexanediol, trans-1,4-cyclohexanedimethanol,cis-1,4-cyclohexanedimethanol, trans-1,3-cyclohexanediol,cis-1,2-cyclohexanediol, trans-1,3-cyclohexanedimethanol, linear orbranched aliphatic diol such as ethylene glycol, 1,3-propanediol,1,4-butanediol, neopentylglycol and ester forming derivatives thereof.

Examples of aromatic mercaptocarboxylic acids, aromatic dithiols,aromatic mercaptophenols and aromatic mercaptonaphthols include aromaticmercaptocarboxylic acid such as 4-mercaptobenzoic acid,2-mercapto-6-naphthoic acid , 2-mercapto-7-naphthoic acid; aromaticdithiol such. as benzene-1,4-dithiol, benzene-1,3-dithiol,2,6-naphthalenedithiol, 2,7-naphthalenedithiol; aromatic mercaptophenolsuch as 4-mercaptophenol, 3-mercaptophenol; aromatic mercaptonaphtholsuch as 6-mercapto-2-naphthol, 7-mercapto-2-naphthol and ester formingderivatives thereof.

In the above description concerning the structural monomer components,the term “alkyl-substituted derivative” means a monomer substituted witha linear or branched alkoxy group which has 1-6 carbon atoms and can beused for introducing an intended structural component into the resin.The term “alkoxy-substituted derivative” means a monomer substitutedwith an alkoxy group which can be used for introducing an intendedstructural component into the resin. The term “halogen-substitutedderivative” means a monomer substituted with halogen atom which can beused for introducing an intended structural component into the resin.The term “ester forming derivative” means a reactive monomer or oligomerwhich can be used for introducing an intended structural component intothe resin by means of esterification reaction. Examples of suitableester forming derivatives include monomer of which the carboxyl group isconverted to alkyl ester or acid halide.

The liquid-crystalline polyester resin comprising the above describedmonomer components may include both of those give anisotropic meltphases and those do not, depending on structural components of thepolyester resin and the ratio thereof, and sequence distribution. Theliquid-crystalline polyester resins used in the present invention arelimited to those exhibit anisotropic melt phases.

Examples of the preferred liquid-crystalline polyester resins includethose having following basic monomer component;

4-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid copolymer;

2-hydroxy-6-naphthoic acid/terephthalic acid/4,4′-dihydroxybiphenylcopolymer;

2-hydroxy-6-naphthoic acid/terephthalic acid/isophthalicacid/4,4′-dihydroxybiphenyl copolymer;

2-hydroxy-6-naphthoic acid/terephthalic acid/isophthalicacid/4,4′-dihydroxybiphenyl/hydroquinone copolymer;

2-hydroxy-6-naphthoic acid/terephthalic acid/hydroquinone copolymer;

4-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid/terephthalicacid/4,4′-dihydroxybiphenyl copolymer;

4-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid/terephthalicacid/hydroquinone copolymer;

2-hydroxy-6-naphthoic acid/2,6-naphthalenedicarboxylicacid/4,4′-dihydroxybiphenyl copolymer;

2-hydroxy-6-naphthoic acid/terephthalic acid/2,6-naphthalenedicarboxylicacid/hydroquinone copolymer;

2-hydroxy-6-naphthoic acid/2,6-naphthalenedicarboxylic acid/hydroquinonecopolymer;

4-hydroxybenzoic acid/2-hydroxy-6-naphthoicacid/2,6-naphthalenedicarboxylic acid/hydroquinone copolymer;

2-hydroxy-6-naphthoic acid/terephthalic acid/2,6-naphthalenedicarboxylicacid/hydroquinone/4,4′-dihydroxybiphenyl copolymer;

2-hydroxy-6-naphthoic acid/terephthalic acid/4-aminophenol copolymer;

4-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid/terephthalicacid/4-aminophenol copolymer;

2-hydroxy-6-naphthoic acid/terephthalicacid-/4,4′-dihydroxybiphenyl/4-aminophenol copolymer;

2-hydroxy-6-naphthoic acid/terephthalic acid/ethylene glycol copolymer;

2-hydroxy-6-naphthoic acid/terephthalicacid/4,4′-dihydroxybiphenyl/ethylene glycol copolymer;

4-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid/terephthalicacid/ethylene glycol copolymer;

4-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid/terephthalicacid/4,4′-dihydroxybiphenyl/ethylene glycol copolymer.

Among the above, preferred liquid-crystalline. polyesters of the presentinvention are those comprising, as structural components, the repeatingunits represented by the following formulae (I) and (II), the repeatingunits represented by the following formulae (II), (III) and (IV) or therepeating units represented by the following formulae (I), (II), (III)and (IV)

 —O—Ar₂—O—  [IV]wherein Ar₁ and Ar₂ represent benzene ring, naphthalene ring, biphenylring, biphenylether ring or biphenyl alkane ring, wherein alkane has 1to 4 carbon atoms, and the rings may be substituted with alkyl group,alkoxy group or halogen atom.

Examples of the above substituents such as alkyl group and alkoxyl groupinclude linear or branched group having 1 l to 6 carbon atoms. Examplesof halogen atoms include fluorine, chlorine, bromine and iodine.

When the repeating units represented by formulae (I) and (II) are used,the molar ratio of (I)/(II) may preferably be 10/90-90/10, morepreferably 20/80-80/20. When the repeating units represented by formulae(II), (III) and (IV) are used, the molar ratio of (II)/(III)+(IV) maypreferably be 90/10-10/90, more preferably 85/15-60/40. When therepeating units represented by formulae (I), (II), (III) and (IV) areused, the molar ratio of (I)/(II) may preferably be as described aboveand the molar ratio of (I)+(II)/(III)+(IV) may preferably be90/10-50/50, more preferably 85/15-60/40.

Examples of monomers used for introducing the repeating unit of formula(I) include 4-hydroxybenzoic acid. Examples of monomers used forintroducing the repeating unit of formula (II) include2-hydroxy-6-naphthoic acid. Examples of monomers used for introducingthe repeating unit of formula (III) includes terephthalic acid and2,6-naphthalenedicarboxylic acid. Examples of monomers used forintroducing the repeating unit of formula (IV) include hydroquinone and4,4′-dihydroxybiphenyl.

The liquid-crystalline polyester resin of the present invention can beprepared by adding an alkaline metal compound, and 2-hydroxy-3-naphthoicacid and/or 2-hydroxynaphthalene-3,6-dicarboxylic acid to the structuralmonomer units of the liquid-crystalline polyester resin before or duringthe polymerizing reaction.

Alternatively, alkaline metal compound, and 2-hydroxy-3-naphthoic acidand/or 2-hydroxynaphthalene-3,6-dicarboxylic acid may be contained inany of the monomers used for preparing the liquid-crystalline polyesterresin. The liquid-crystalline polyester resin of the present inventioncan be prepared by copolymerizing the monomer containing the alkalinemetal compound, and 2-hydroxy-3-naphthoic acid and/or2-hydroxynaphthalene-3,6-dicarboxylic acid and the other polymerizingmonomers.

When alkaline metal compound, and 2-hydroxy-3-naphthoic acid and/or2-hydroxynaphthalene-3,6-dicarboxylic acid are contained in a monomercomponent, the preferable monomer is 2-hydroxy-6-naphthoic acid. Inparticular, 2-hydroxy-6-naphthoic acid preferably includes alkalinemetal compound in an amount of 50-5000 ppm as alkaline metal and2-hydroxy-3-naphthoic acid and/or 2-hydroxynaphthalene-3,6-dicarboxylicacid in an amount of 50-10000 ppm.

The method for preparing the liquid-crystalline polyester resin of thepresent invention is not limited and any known method can be employed.For example, conventional polymerization method such as moltenacidolysis method and slurry polymerization method for preparing apolyester to give ester bondings among the above described monomercomponents may be employed.

The molten acidolysis method is preferably used for the presentinvention. In this method, the polymerizing monomers are heated to givemolten solution of the reactants and then the solution is reacted togive the molten polymer. The final step of this method may be carriedout under vacuum to facilitate removal of the volatile by-products suchas acetic acid or water.

The slurry polymerization method is characterized in that monomers arereacted in a heatexchange fluid to give solid state polymer in the formof suspension in the heatexchange liquid medium.

In either of the molten acidolysis method or the slurry polymerizationmethod, the polymerizing monomer components used for the preparation ofthe liquid-crystalline polyester resin may be in the denatured form,i.e. in the form of lower acyl esters, that obtained by esterifying thehydroxyl group at room temperature. The lower acyl group may havepreferably 2-5, more preferably 2-3 carbon atoms. Acetic esters are mostpreferably used for the reaction.

The lower acyl esters of the monomers may be those prepared beforehandby acylating the monomers independently or may be those produced in thereaction system by adding an acylating agent such as acetic anhydride tothe monomers upon preparing the liquid-crystalline polyester.

In either of the molten acidolysis method or the slurry polymerizationmethod, a catalyst may be used in the reaction, if desired.

Examples of the catalysts include organic tin compounds such as dialkyltin oxide (ex. dibutyl tin oxide) and diaryl tin oxide; organic titaniumcompounds such as titanium dioxide, alkoxy titanium silicate andtitanium alkoxide; antimony trioxide; alkaline or alkaline earth metalsalt of carboxylic acid such as potassium acetate; and gaseous acidcatalysts such as Lewis acid (ex. BF₃) and halogenated hydrogen (ex.HCl).

When a catalyst is used, the amount of the catalyst added to thereaction based on the total monomers may preferably be 10-1000 ppm, andmore preferably 20-200 ppm.

Preferably, the liquid-crystalline polyester resin of the presentinvention is that log viscosity of the same can be measured inpentafluorophenol. The log viscosity of the polymer measured at aconcentration of 0.1 g/dl in pentafluorophenol at 60° C. may preferablybe 0.3 dl/g or above, more preferably 0.5-10 dl/g, most preferably 1-8dl/g.

The melting viscosity of the liquid-crystalline polyester resin of thepresent invention measured with capillary rheometer at a temperature 30°C. higher than the melting point of the resin may preferably be 1-1.000Pa.s, more preferably 5-300 Pa.s.

The present invention further provides a liquid-crystalline polyesterresin composition comprising the above-described liquid-crystallinepolyester resin. The liquid-crystalline polyester resin composition maybe those obtained by admixing one or more filler and/or reinforcingagent to the liquid-crystalline polyester resin. The form of the fillerand/or reinforcing agent may be any of conventional reinforcing agentsand/or fillers for resin compositions such as fibrous, plate orparticulate form.

Examples of fibrous fillers and reinforcing agents may include glassfiber, silica-alumina fiber, alumina fiber, carbon fiber and aramidfiber. Among them, glass fiber is preferably used because of its goodbalance of physical properties and cost.

Examples of plate or particulate fillers may include talc, mica,graphite, wollastonite, calcium carbonate, dolomite, clay, glass flake,glass beads, barium sulfate and titanium oxide.

The fillers and/or reinforcing agents may be added to theliquid-crystalline polyester resin composition in an amount of 0-100parts by weight, especially 20-70 parts by weight to 100 parts by weightof the liquid-crystalline polyester resin. If the amount of the fibrous,plate and/or particulate inorganic filler is more than 100 parts byweight, the moldability of the resulting liquid-crystalline polyesterresin composition tends to be decreased or the exhausting of thecylinder or die of the molding device tends to be increased.

The liquid-crystalline polyester resin composition according to thepresent invention may further be admixed with one or more additivesconventionally used for resin compositions, if desired, for examplemolding lubricant such as higher aliphatic acid, higher aliphatic ester,higher aliphatic amide, higher aliphatic acid metal salt, polysiloxaneand fluorocarbon resin; colorant such as dyes and pigments; antioxidant;thermal stabilizer; UV absorbent; antistatic agent and surface activeagent.

Additionally, an agent which provides an exterior lubricant effect suchas higher aliphatic acid, higher aliphatic ester, higher aliphatic acidmetal salt or fluorocarbon-type surfactant may be added to the pelletsof the liquid-crystalline polyester resin or the liquid-crystallinepolyester resin composition according to the present invention, so thatthe agent adhere to the surface of the pellet, before subjecting thepellets to the injection-molding process.

To the liquid-crystalline polyester resin composition of the presentinvention, one or more resin components other than those described asabove may be added. Examples of other resin components includethermoplastic resins such as polyamide, polyester, polyphenylenesulfide, polyether ketone, polycarbonate, polyphenylene ether anddenatured derivatives thereof, polysulfone, polyethersulfone andpolyether imide and thermosetting resins such as phenol resin, epoxyresin and polyimide resin.

The liquid-crystalline polyester resin composition of the presentinvention may be obtained by adding fillers, reinforcing agents andother resin components to the polyester resin and melt kneading themixture at a temperature from near the melting point of the polymer tothe melting point plus 100° C. using a kneading machine such as Banburymixer, kneader, single screw extruder, twin screw extruder or the like.

The liquid-crystalline polyester resin or the liquid-crystallinepolyester resin composition according to the present invention may bemolded using a conventional melt molding process, preferably injectionmolding, compression molding, extrusion molding and blow molding. Themolded article, film and fiber obtained with the liquid-crystallinepolyester resin of the present invention are particular useful for partsof electric and electronic devices, machines and automobiles.

EXAMPLES

The present invention is further described in reference to the followingExamples. The following examples are intended to illustrate theinvention and are not to be construed to limit the scope of theinvention.

In the examples, following abbreviations are used.

LCP: liquid-crystalline polyester

BON3: 2-hydroxy-3-naphthoic acid

BON3,6: 2-hydroxynaphthalene-3,6-dicarboxylic acid

Monomers Used

POB: 4-hydroxybenzoic acid, which may contain less than 1 ppm (detectedby atomic absorption spectrometry) of alkaline metal.

BON6: 2-hydroxy-6-naphthoic acid, which may contain below the detectionlimit (by means of high-performance liquid chromatography) of BON3 andBON3,6 and which may contain less than 1 ppm (detected by atomicabsorption spectrometry) of alkaline metal.

TPA: terephthalic acid, which may contain less than 1 ppm (detected byatomic absorption spectrometry) of alkaline metal.

HQ: hydroquinone, which may contain less than 1 ppm (detected by atomicabsorption spectrometry) of alkaline metal.

NDA: 2,6-naphthalenedicarboxylic acid, which may contain less than 1 ppm(detected by atomic absorption spectrometry) of alkaline metal.

Polymerizing Condition

-   <Polymerizing Condition-1>

The polymerizing condition of LCP-1 comprising 4-hydroxybenzoic acid and2-hydroxy-6-naphthoic acid in the ratio of 70/30 (mol %) is describedbelow.

POB and BON6 in the ratio of LCP-1 shown as above were fed in a reactioncontainer equipped with an agitating device with torque-meter andcondenser so that the total monomer amount was 7.5 mol. Then aceticanhydride of 1.025 fold moles to the total monomers was added to thecontainer. Under the nitrogen atmosphere, the mixture was heated to 150°C. and kept at the temperature for 30 minutes, then rapidly heated to190° C. with distilling out the by-product acetic acid and kept at thetemperature for 1 hour. Then the mixture was heated to 320° C. over 3.5hours and the pressure was reduced to 20 mmHg over about 30 minutes.When the torque became the predetermined level, the polymerizingreaction was terminated. The resulting resin was removed from thecontainer by a taking off means and crushed to give pellets. As aresult, approximately theoretical amount of acetic acid was distilledout.

-   <Polymerizing Condition-2>

The polymerizing condition of LCP-2 comprising 4-hydroxybenzoic acid,2-hydroxy-6-naphthoic acid, terephthalic acid and hydroquinone in theratio of 60/18/11/11 (mol %) is described below.

POB, BON6, TPA and HQ in the ratio of LCP-2 shown as above were fed in areaction container. The polymerizing condition was the same ascondition-1 except for that the mixture was kept at 190° C. for 1 hourand heated to 360° C. over 3.75 hours.

-   <Polymerizing Condition-3>

The polymerizing condition of LCP-3 comprising 4-hydroxybenzoic acid,2-hydroxy-6-naphthoic acid, naphthalenedicarboxylic acid andhydroquinone in the ratio of 65/5/15/15 (mol %) is described below.

POB, BON6, NDA and HQ in the ratio of LCP-3 shown as above were fed in areaction container. The polymerizing condition was the same ascondition-1 except for that the mixture was kept at 190° C. for 1 hourand heated to 360° C. over 3.75 hours.

Coloring of LCP and Method For Preparing Test Pieces

The liquid-crystalline polyester resin obtained by polymerizing reactionwas molten kneaded with carbon black (Mitsubishi carbon black #45,Mitsubishi Chemical Corporation) to give colored liquid-crystallinepolyester resin. In this coloring process, twin screw extruder PCM-30(Ikegai Corporation) was used. The amount of carbon black used was 1part by weight to 100 parts by weight of the resin pellet. Then themixture was pelletized with strand-cutter.

Thus obtained black colored pellets were molded with injection molderMINIMAT 26/15 (Sumitomo Heavy Industries, Ltd.) (Cylinder temperature:350-350-310-280° C., die temperature: 70° C.) to give strip shapedbending test pieces of 12.7×64×3.0 (mm).

The Method For Evaluating the Brightness of Color

The strip shaped bending test piece was set in the window frame (10×7.5mm φ) of spectrophotometer (MACBETH COLOR-EYE 7000, Sakata InxCorporation) and the L*, a* and b* values were measured. The value L*shows the brightness of color and the lower L* value means the testpiece is well colored in black. Accordingly, this value was used forevaluating the colorability of the resin.

The Method For Determining Izod Impact Value

Izod impact value was measured using strip shaped bending test piecesbased on ASTM D256.

Example 1

The monomer components of LCP-1, BON3 and potassium sulfate were fed ina reaction container so that, at the beginning of the polymerization,the content of BON3 residue in the resin was 500 mmol % and the contentof potassium sulfate calculated as the amount of potassium in the resinwas 200 ppm. The polymerization and acetic acid distillization reactionwas conducted by the method according to polymerizing condition-1. Thecolorability and Izod impact value of the resulting liquid-crystallinepolyester resin were measured. The potassium content of the pelletobtained after polymerization measured by atomic absorption spectrometrywas 206 ppm.

Example 2

Polymerization and evaluation were conducted according to the method ofExample 1 except for that BON3,6 was added instead of BON3 so that thecontent of BON3,6 residue in the resin was 700 mmol % at the beginningof the polymerization. The potassium content of the liquid-crystallinepolyester resin pellet obtained after polymerization measured by atomicabsorption spectrometry was 203 ppm.

Example 3

Polymerization and evaluation were conducted according to the method ofExample 1 except for that BON3,6 was added in addition to BON3 so thatthe-contents of BON3 and BON3,6 residues in the resin were 500 mmol %and 700 mmol % respectively at the beginning of the polymerization. Thepotassium content of the liquid-crystalline polyester resin pelletobtained after polymerization measured by atomic absorption spectrometrywas 201 ppm.

Example 4

The monomer components of LCP-2, BON3, BON3,6 and potassium sulfate werefed in a reaction container so that, at the beginning of thepolymerization, the contents of BON3 and BON3,6 residues in the resinwere 800 mmol % and 1000 mmol % respectively and the content ofpotassium sulfate calculated as the amount of potassium in the resin was400 ppm. The polymerization and acetic acid distillization reaction wasconducted by the method according to polymerizing condition-2. Thecolorability and Izod impact value of the resulting liquid-crystallinepolyester resin were measured according to the method of Example 1. Thepotassium content of the pellet obtained after polymerization measuredby atomic absorption spectrometry was 399 ppm.

Example 5

The monomer components of LCP-3, BON3, BON3,6 and potassium sulfate werefed in a reaction container so that, at the beginning of thepolymerization, the contents of BON3 and BON3,6 residues in the resinwere 500 mmol % and 600 mmol % respectively and the content of potassiumsulfate calculated as the amount of potassium in the resin was 250 ppm.The polymerization and acetic acid distillization reaction was conductedby the method according to polymerizing condition-3. The colorabilityand Izod impact value of the resulting liquid-crystalline polyesterresin were measured according to the method of Example 1. The potassiumcontent of the pellet obtained after polymerization measured by atomicabsorption spectrometry was 249 ppm.

Comparative Example-1

The monomer components of LCP-1 and potassium sulfate were fed in areaction container so that, at the beginning of the polymerization, thecontent of potassium sulfate calculated as the amount of potassium inthe resin was 300 ppm. The polymerization and acetic acid distillizationreaction was conducted by the method according to polymerizingcondition-1. The colorability and Izod impact value of the resultingliquid-crystalline polyester resin were measured according to the methodof Example 1. The potassium content of the pellet obtained afterpolymerization measured by atomic absorption spectrometry was 303 ppm.

Comparative Example-2

The monomer components of LCP-1, BON3 and BON3,6 were fed in a reactioncontainer so that, at the beginning of polymerization, the contents ofBON3 and BON3,6 residues in the resin were 300 mmol % and 400 mmol %respectively. The polymerization and acetic acid distillization reactionwas conducted by the method according to polymerizing condition-1. Thecolorability and Izod impact value of the resulting liquid-crystallinepolyester resin were measured according to the method of Example 1. Thepotassium content of the pellet obtained after polymerization measuredby atomic absorption spectrometry was 2 ppm.

Comparative Example-3

The monomer components of LCP-1, BON3,6 and potassium sulfate were fedin reaction container so that, at the beginning of the polymerization,the content of BON3,6 residue in the resin was 7000 mmol % and thecontent of potassium sulfate calculated as the amount of potassium inthe resin was 200 ppm. The polymerization and acetic acid distillizationreaction was conducted by the method according to polymerizingcondition-1. The colorability and Izod impact value of the resultingliquid-crystalline polyester resin were measured according to the methodof Example 1. The potassium content of the pellet obtained afterpolymerization measured by atomic absorption spectrometry was 200 ppm.

Comparative Example-4

The monomer components of LCP-1, BON3 and potassium sulfate were fed ina reaction container so that, at the beginning of the polymerization,the content of BON3 residue in the resin was 8000 mmol % and the contentof potassium sulfate calculated as the amount of potassium in the resinwas 200 ppm. The polymerization and acetic acid distillization reactionwas conducted by the method according to polymerizing condition-1. Thecolorability and Izod impact value of the resulting liquid-crystallinepolyester resin were measured according to the method of Example 1. Thepotassium content of the pellet obtained after polymerization measuredby atomic absorption spectrometry was 199 ppm.

Comparative example-5

The monomer components of LCP-2 and potassium sulfate were fed in areaction container so that, at the beginning of the polymerization, thecontent of potassium sulfate calculated as the amount of potassium inthe resin was 5000 ppm. The polymerization and acetic aciddistillization reaction was conducted by the method according topolymerizing condition-2. The colorability and Izod impact value of theresulting liquid-crystalline polyester resin were measured according tothe method of Example 1. The potassium content of the pellet obtainedafter polymerization measured by atomic absorption spectrometry was 5005ppm.

Comparative example-6

The monomer components of LCP-3 and BON3 were fed in a reactioncontainer so that, at the beginning of the polymerization, the contentof BON3 residue in the resin was 400 mmol %. The polymerization andacetic acid distillization reaction was conducted by the methodaccording to polymerizing condition-3. The colorability and Izod impactvalue of the resulting liquid-crystalline polyester resin were measuredaccording to the method of Example 1. The potassium content of thepellet obtained after polymerization measured by atomic absorptionspectrometry was 1 ppm.

These results are shown in the following table 1. TABLE 1 ExampleComparative example 1 2 3 4 5 1 2 3 4 5 6 composition Basic compositionLCP-1 LCP-1 LCP-1 LCP-2 LCP-3 LCP-1 LCP-1 LCP-1 LCP-1 LCP-2 LCP-3 BON3,6 content^(※) — 700 700 1000 600 — 400 7000 — — — (mmol %) BON3content^(※) 500 — 500 800 500 — 300 — 8000 — 400 (mmol %) Potassiumcontent 206 203 201 399 249 303  2  200  199 5005  1 (PPM) property L* 33  32 34 32 33  36  39  39  37  39  40 IZOD impact value 426 432 414412 388 291 207  53  78  255 188 (J/M)(note)^(※)The content is the concentration in the resin calculated from theamount of each component fed to the reaction containerIndustrial Applicability

The liquid-crystalline polyester resin of the present invention has goodcolorability, improved heat resistance and good mechanical properties.The liquid-crystalline polyester resin and the composition comprisingthe polyester resin of the present invention may be molded using aconventional molding process, preferably injection molding, compressionmolding, extrusion molding and blow molding. The molded article obtainedwith the liquid-crystalline polyester resin of the present inventionsuch as injection molded article, film and fiber is particular usefulfor parts of electric and electronic devices, machines and automobiles.

1. A liquid-crystalline polyester resin which comprises monomer unitsderived from 2-hydroxy-3-naphthoic acid and/or2-hydroxynaphthalene-3,6-dicarboxylic acid in an amount of 1-5000 mmol %based on the total monomer components of the resin and an alkaline metalcompound in an amount of 10-3000 ppm as alkaline metal based on thetotal monomer components of the resin.
 2. The liquid-crystallinepolyester resin according to claim 1, wherein said alkaline metal ispotassium and/or sodium.
 3. The liquid-crystalline polyester resinaccording to claim 1, wherein said alkaline metal compound is one ormore salt(s) selected from the group consisting of sulfate, carbonate,bicarbonate, nitrate, carboxylate and haloid of alkaline metal.
 4. Theliquid-crystalline polyester resin according to claim 3, wherein themean volume diameter of the alkaline metal salt in the resin is 0.01-500μm.
 5. The liquid-crystalline polyester resin according to claim 1,wherein the resin comprises the repeating units represented by thefollowing formulae (I) and (II), the repeating units represented by thefollowing formulae (II), (III) and (IV) or the repeating unitsrepresented by the following formulae (I), (II), (III) and (IV)

—O—Ar₂—O—  [IV] wherein Ar₁ and Ar₂ represent benzene ring, naphthalenering, biphenyl ring, biphenylether ring or biphenyl alkane ring, whereinalkane has 1 to 4 carbon atoms, and the rings may be substituted withalkyl group, alkoxy group or halogen atom.